The invention relates a connection fitting with a fitting body or a connection body, which directly by itself or indirectly has a rotatable attachment device, such as threads or a bayonet (quarter-turn) fastener and at least one seal. The fitting may be, for example, a drain plug for radiators or other liquid containers, ventilation valve, pipe connector, lid, stop insert, support sheath and/or clamping ring for a pipe screw fitting or the like. The fitting or connection body and the seal are a multi-component plastic part, in which the fitting or connection body is made of the harder plastic component and the seal is made out the other softer plastic component.
Connection fittings of this type are known in various forms depending on the application. For example, there are known drain plugs for radiators or according to German patent DE 44 40 852 C1 for other liquid containers, or a ventilation valve according to German utility model DE 297 15 018, or a pipe connector according to German patent DE 27 15 525 C2, or a lid according to published German patent application DE 195 08 509 A1. In these cases or even other comparable arrangements, the actual fitting body is made of the hard plastic and the seal is made of the soft plastic. Consequently, the handling of such of connection fittings of the above type is simple for the user.
From German utility model G 93 15 601.4 and from German patent DE 44 03 702 C2, FIG. 16, connection fittings with fitting or connection bodies are known in the form of stop inserts for pipes to be connected. The inserts could be made of plastic and not have an attachment device themselves, such as a thread, but are instead attached indirectly via swivel nuts and counterparts, and also have seals made of softer materials on their stop and/or an accompanying support sheath.
It has proven to be useful that for different applications, the seal can be damaged by the opposing surface, if this opposing surface is rough or uneven, has impurities due to residual shavings, or even has a burr. If the connection fitting is rotated for its attachment, in order to bring its screw thread or its bayonet fastener into the corresponding mounting position, a relative rotation between the seal and the opposing surface can occur and rub the seal via an opposing surface, which under certain circumstances is uneven, fissured, or contaminated. In this way, the seal can be considerably damaged.
It is therefore an object of the invention to create a fitting with a seal in a multi-component plastic design, in which an advantage is manufacture in an injection molding tool or spray operation and/or the advantage is retained. The user practically only has to mount a single part. In spite of this, however, when screwing in this fitting, the seal cannot be destroyed or damaged by the opposing surface.
In order to achieve this apparently contradictory purpose, the connection fitting described at the outset is wherein the two different plastic components that form the fitting are plastics which are incompatible with each other, and the seal manufactured together with the fitting or connection body is arranged in the axial direction on the fitting or connection body in a form-fitting manner, but movable in the rotation direction, i.e. rotatable relative to the fitting or connection body.
The invention thus makes use of the discovery that in manufacturing a multi-component object made of incompatible plastics, they are in fact manufactured together in an advantageous way, and can thereby be connected to each other directly during manufacture, but in spite of this do not adhere to each other. In a suitable shape the seal can thus be manufactured with the fitting or connection body (hereinafter just xe2x80x9cfitting bodyxe2x80x9d for the sake of simplicity) in the injection molding process and can then be rotated relative to the fitting body, so that when screwing the fitting in and upon contact of the seal with an uneven and fissured opposing surface, the seal does not turn along with the fitting body when it is rotated further, and thereby avoids too great a damage to the seal. In this way, an axial form-fit in one direction, namely opposite the tightening or inward rotating direction, is sufficient.
It is expedient if the fitting body is made of polyacetal (polyoxymethylene or POM) and the seal is made of a thermoplastic elastomer or of rubber, such as EPDM, or of silicone. POM is a hard, durable plastic, which is suitable for the purpose of forming a fitting body with threads or a bayonet fastener even for rugged applications, and which has a very small water absorption capacity, thus allowing a long lifetime even during an application in heater construction on radiators or heater lines having extreme temperature fluctuations. Thermoplastic elastomers or rubber or silicone, in contrast, are reliable materials for seals, which however can be manufactured in one injection molding operation together with the fitting body, so that a subsequent mounting occurs in an advantageous way. Since these different plastics are, however, respectively incompatible with each other, it results that even during the manufacturing of the fitting, the two parts are not firmly affixed and melted to each other, as is the case for otherwise customary multi-component plastic parts, but instead the sealing ring can be rotated or held firmly in a ring groove in the fitting body that has been recessed especially for it, while the fitting can be rotated relative to the sealing ring. Thus, during the attachment of the connection fitting using threads or a bayonet fastener, an impairment or damage to the seal is then also avoided if the opposing seal surface has cut or scraped projections or similar uneven areas.
It is expedient if the ring-shaped seal has at least one recess or ring groove running around its sealing area and is flexible in the axial direction in the area of this recess or ring groove. By such a ring groove opening on the free circumference of the seal, it results that the seal can be compressed in the axial direction, not only because of its soft material, but also because of this shape. The seal can adapt correspondingly well to the unevenness of the opposing seal surface.
It is beneficial in the process if the radial depth of the recess or ring groove is approximately equal to or smaller than the radial overhang of the non-deformed seal in comparison to the outer diameter of the thread of the fitting body. In the thread area, the seal is then compact and suitably stable, while the overhang that functions above all for sealing against an opposing surface has the desired flexibility and adaptability.
In a connection fitting of the above type with a thread and a stop arranged in the tightening direction behind the thread, the seal can be arranged in the progression of the thread or between the thread and the stop. Especially the latter case is frequently applied for drain plugs, blind plugs, ventilation valves, pipe connections, pipe screw connections, etc.
When screwing a connection fitting of this type into an opposing part that has a corresponding opposing thread, this opposing part comes into contact with seal, so that the seal can then rotate relative to the connection fitting or instead relative to this opposing part, depending on where the smaller friction occurs. If the friction is too great between the seal and the opposing surface because of uneven areas, projections or sharp edges, the seal will stay in place relative to the further rotating connection fitting, thus not rotating along with it, so that damage and leaks resulting therefrom are largely excluded.
The seal can also be arranged, in a connection fitting of another type, between a stop and a bayonet fastener of the fitting body. A similar operating method thereby results as in an arrangement on a connection fitting with threads.
Especially with combination of individual or several of the features and measures described above, a connection fitting results in any desired adaptation to different uses, for example as a pipe connection, drain plug, ventilation valve, or the like, in which the fitting body and the seal constructed as a sealing ring are already connected to each other during manufacture. Thus, a subsequent mounting of the sealing ring onto the fitting is avoided, but nevertheless the sealing ring can be rotated relative to the fitting body, so that upon contact with an opposing surface that is damaging to the sealing ring under certain circumstances, such a relative movement between the sealing ring and the opposing surface can be avoided, in that this relative movement is transferred to the fitting body.